Multi-CPU Qbus VAXen

If you mean 4-way multiprocessing, then 2-way was almost certainly done at some time (probably in DECwest). I'm not sure 4-way is practical, at least not with 4 backplanes. If you want them all in one backplane you probably have to remove (or otherwise inhibit) the bus terminating resistors on 3 of the processors. As others have pointed out, it doesn't really get you anywhere since there is no real shared memory between the processors (they could each have their own via PMI or they could all share some Qbus memory - neither is an appealing option). You would also have the minor problem that no OS would be able to do much with the slave processors. (In fact, I think all the Oses I know of probably wouldn't even notice them, so they would probably boot as though they were on a MicroVAX II (or III if you used KA65x processors). If OTOH you meant 4 separate BA23 boxes each with its own processor all in a VAXcluster, then that's just independent MicroVAXes ... I had racks like that in the lab at DEC. But that's less exciting than pushing the boundaries I guess. You don't need a hacked cab, just an ordinary 19" rack will do ... I kept back-to-back VAX 4000s or MicroVAX IIIs in the bottom to save space and make *absolutely* sure the rack could not be tipped :-) Antonio -- --------------- Antonio Carlini arcarlini(a)iee.org